Launch a .Net app from Ext JS.

I am rewriting a JSP into Ext JS.

In the JSP, it will launch a third party .Net app window by doing a response.sendRedirect(URL). I also verified by typing the URL directly in the browser address and it successfully launched the .Net app.

Naively I am trying to put this in the EXT JS Client side by doing a listener:
this.sm = new Ext.grid.RowSelectionModel({
singleSelect:true,
listeners:{
rowselect:function(sm,rowIndex,rec){
var url ="http://localhost:80/lauchDotNet.application";
var Win = new Ext.Window({
autoLoad: url
});
Win.show();
}
}
}
});
This will launch a browser window with lots of texts, not a .Net application I was expecting.

I also tried to put the URL to be a jsp that does the response.sendRedirect(URL) but got the same result.